An LED (Light Emitting Diode) is a semiconductor device that can realize various colors by forming a light emitting source using compound semiconductor materials such as GaAs, AlGaAs, GaN, InGaN, AlGaInP, and so on. The LEDs are manufactured as a type of a surface mount device (SMD) directly mounted on a PCB in accordance with the trend of miniaturizing and slimming down devices. The LEDs of the SMD type are gradually replacing existing lighting devices and widening the extent of the use thereof.